1. Field of the Invention
The present invention relates to a laser irradiation device, a patterning method and a method of fabricating an Organic Light Emitting Display (OLED) using the laser irradiation device, and more particularly, to a laser irradiation device, a patterning method and a method of fabricating an OLED using the method that are capable of partially adjusting laser density by providing a mask including a Fresnel lens for changing an optical path.
2. Description of the Related Art
In general, an Organic Light Emitting Display (OLED) among flat panel displays includes an anode electrode, a cathode electrode, and organic layers disposed between the anode and cathode electrodes. Each of the organic layers includes at least an emission layer. The OLED is classified into a polymer OLED and a small molecule OLED depending on the materials constituting the emission layers.
In order to realize a full color OLED, each of emission layers representing the three primary colors of red (R), green (G) and blue (B) must be patterned. In the case of the small molecule OLED, a method of patterning the emission layer uses a shadow mask, and in the case of the polymer OLED, an inkjet printing method or a Laser Induced Thermal Imaging (LITI) method is used. Among them, the LITI method can finely pattern the organic layer, and can easily realize a high resolution and large-sized display. Moreover, preferably, the LITI method is a dry process, whereas the inkjet printing method is a wet process.
In a method of fabricating an Organic Light Emitting Display (OLED) using a laser irradiation device, a substrate is provided, and a donor substrate having an organic layer is laminated on the substrate. Laser radiation is focused on a predetermined portion of the donor substrate through a laser irradiation device. The laser irradiation device includes a light source, a patterned mask, and a projection lens.
In this process, the laser radiation emitted by the light source passes through the patterned mask to the projection lens. The laser radiation is directed to the projection lens along a pattern formed on the mask. Then, the laser radiation is refracted through the projection lens and then irradiated onto the donor substrate in a shape of the pattern of the mask, thereby forming an organic layer pattern on the substrate.
In this process, a portion of the organic layer attached to the donor substrate and receiving the laser radiation, is separated from the donor substrate by the laser radiation and transferred to the substrate, and other portions' of the organic layer, which do not receive the laser radiation, are left on the donor substrate to form the organic layer pattern on the substrate. That is, connection between the portion receiving the laser radiation and the other portions not receiving the laser radiation is broken to form the organic layer pattern.
Then, an upper electrode is formed on the organic layer pattern to fabricate the OLED.
A uniform intensity of laser radiation is irradiated along the entire irradiated region. The intensity of the laser radiation required to cut the connection in the organic layer must be higher than that of the laser radiation required to separate and transfer the organic layer from the donor substrate. Eventually, laser radiation with a high intensity is applied to the organic layer in order to transfer the organic layer. Therefore, laser radiation with a high intensity is required in order to transfer the organic layer, and the laser radiation with a high intensity can damage the organic layer. On the other hand, when low intensity laser radiation is irradiated, a connection in the organic layer is insufficiently cut to make it difficult to obtain a uniform organic layer pattern.